Perimeter of a Cylinder

[w***@afc-holcroft.com]

I was told that an Enhancement Request was needed for this occurance,
so I submitted one. Be aware of this.

If you select the face of a rectangular plate, then use the Measure
Tool a set of values will be shown. One of the values is Perimeter.
As expected the value is the sum of the outer edges of the selected
surface. This is well defined in all Geometry Texts that I know of.

Now if you select the outer curved face of a cylinder (not the end) and
use the Measure Tool an identical set of data is presented. One of the
values is Perimeter. The calculated value is actually 2*PI*diameter.
What the heck is this?

The definition that Solidworks uses for Perimeter is the sum of the
outer bounding edges. The definition that is used in all Geometry
Texts is the sum of all outer bounding edges of a two-dimensional
shape.

My request is that they remove the Perimeter value if this selection is
chosen. Is there anyone else that would agree?

[Dale Dunn]

Post by w***@afc-holcroft.com
The definition that Solidworks uses for Perimeter is the sum of the
outer bounding edges. The definition that is used in all Geometry
Texts is the sum of all outer bounding edges of a two-dimensional
shape.

It IS 2-dimensional, just not in a flat space. This makes sense, and I
think the current behaviour should be kept, rather than removing the
capacity. Perhaps change "perimiter" to "length of all edge loops" to
emphasize the difference.

[CS]

I agree that it would be easy to overlook that it is calculating both edges.
What you are looking for is it's circumference correct. Maybe they just
need a change in terminology.
Perimeter could be

Total length of edges:

and I think it would be beneficial to add

Circumference:

You have to remember that not all cylinders have square bottoms. And who is
to actually say which end you would want to use as the Perimeter.

Corey

Post by Dale Dunn

Post by w***@afc-holcroft.com
The definition that Solidworks uses for Perimeter is the sum of the
outer bounding edges. The definition that is used in all Geometry
Texts is the sum of all outer bounding edges of a two-dimensional
shape.

It IS 2-dimensional, just not in a flat space. This makes sense, and I
think the current behaviour should be kept, rather than removing the
capacity. Perhaps change "perimiter" to "length of all edge loops" to
emphasize the difference.

[Edward T Eaton]

The perimeter of a sphere is 0.000", so at least they are consistent. I
would rather have consistency then ask them to write exceptions for
different geoemetry - that seems like we'd just be begging for trouble.
But I see the point about the confusion - a square with a hole in the middle
of it has a larger perimeter than the square itself, and I think I might
make a bad assumption if I wasn't paying attention.

If you are going to go into enhancment requests, I like Corey's suggestion
of changing the term to 'total length of edges' because that is what is
measured. <Maybe> its worth adding the possbility of adding a second
'perimeter' calcuation that would only apply to outer loops of a face. Much
of hte time, perimeter would be the same as total length of edges.
Cylinders, spheres, and other similar shapes would deliver a perimeter of
'n/a'

Anyway, neat observation!

Post by CS
I agree that it would be easy to overlook that it is calculating both edges.
What you are looking for is it's circumference correct. Maybe they just
need a change in terminology.
Perimeter could be
and I think it would be beneficial to add
You have to remember that not all cylinders have square bottoms. And who is
to actually say which end you would want to use as the Perimeter.
Corey

Post by Dale Dunn

Post by w***@afc-holcroft.com
The definition that Solidworks uses for Perimeter is the sum of the
outer bounding edges. The definition that is used in all Geometry
Texts is the sum of all outer bounding edges of a two-dimensional
shape.

It IS 2-dimensional, just not in a flat space. This makes sense, and I
think the current behaviour should be kept, rather than removing the
capacity. Perhaps change "perimiter" to "length of all edge loops" to
emphasize the difference.